Tuesday, June 12, 2012

Lomatium ravenii, Hunzinger Flat, Lassen County, California?

NDDB EO#32 Lomatium ravenii at this site was
reported in first in 2003, without citation of a voucher specimen, and without
any subsequent revisits. On June 6, 2012
I visited the site, and having also visited the type locality for L. ravenii (1 mile S of Ravendale) and
nearby sites, am uncertain of the taxon of Lomatium
present at NDDB EO#32 (1/4 mile N Hunzinger
Flat, Lassen County, 41.09199 - 120.78617)

Lomatium ravenii was described by Mathias & Constance
(1959). It was treated as distinct by
Constance (1993). Cronquist (1997),
however, did not recognize L. ravenii:
rather, he submerged it within a wholesale variable and geographically
widespread L. nevadense (with a
geographic range over most of the northern Great Basin).

At the type
locality of L. ravenii, and at nearby
reported sites on the Madeline Plains, Lassen County, plants answering to L. ravenii have leaves that are subtly
but distinctly different from the plants at NDDB EO#32, being more finely dissected [that is, upon morphometric analysis, cf. Carlson et al. 2011, would a) show a greater bifurcation ratio, and b) would have linear, fewer lobed terminal leaflet segments as compared to topotype material of L. ravenii). Published manuals use flower color to
distinguish taxa of Lomatium, and
because these plants flower very early (often before regional road networks are
passable and snowfree) flower color is often not evident on herbarium specimens. The plants at NDDB
EO#32 did not have purple flowers, but because flower color fades quickly in
the yellow flowered taxa, such that spent flowers of both yellow and white
flowered taxa appear similar in senescence, flower color of NDDB EO#32 was not
evident on my visit. (I will also comment here than central Nevada material at NY attributed does not match the type of L. ravenii, and is probably undescribed)

Taxonomy of
Great Basin Lomatium allied to L. nevadense is not resolved. Lomatium
ravenii has been attributed to a range across most of the central Great
Basin (Constance & Weatherwax 2012).
However, plants allied to this group from eastern Oregon have been shown
to be a distinct species, L. bentonitum
(Carlson et al. 2011).

My specimen of
NDDB EO#32 is more similar in leaf morphology to L. foeniculaceum var. macdougalii,
as treated in TJM2 (Constance & Weatherwax 2012), at least compared to
material attributed to this taxon from near Alturas, and material from central
Oregon. There is a unprocessed record
for L. ravenii for the Lane Reservoir
quadrangle, and if a second site is known, would be important to voucher if
appropriate. Notable in this regard that
many reported occurrences of L. foeniculaceum
var. macdougalii and L. ravenii from Modoc and Lassen
counties are not vouchered.

A salient
habitat difference pertaining to site occupancy for L. foeniculaceum var. macdougalii
versus L. ravenii is related to
substrate. Lomatium ravenii, at least the type population, and other
populations on the Madeline Plains, occur on fine, clay and silt, subalkaline lacustrine
and aeolian deposits that form deep soils on sites that are seasonally flooded
in the exceptional, infrequent wet year (see photo on Calphotos). By contrast, L. foeniculaceum var. macdougalii
occurs on tehpra deposits (material that falls out of the air associated with
explosive vulcanism events). At NDDB
EO#32 the deposit is a volcaniclastic tephra that was entrained within a
mudflow, which subsequently set. The parent material at the site has weathered
sufficiently to have a high clay component in the soil. However, the site is not subalkaline, but
rather the soils are slightly acidic.
By contrast, the soil pH at sites I visited for L. ravenii ranged from 7.5 to 8.1 .
This habitat contract is suggestive that the plants at EO#32 are L. foeniculaceum var. macdougalii rather than L. ravenii.

It should be noted
here that the revised Jepson Manual treatment attributed to Lincoln Constance
was not extensively changed from his 1993 treatment (since he was not active by
1999 and died in 2001). That fact posits
the problem that some California endemic taxa would benefit from additional
study, which, along with the recent description of other novel, narrowly
endemic, rare taxa of Lomatium from
the arid western U.S. (Helliwell 2010, Darrach & Wagner 2011, Darrach et
al. 2011), suggests further study of the
entire genus is suggested, and that determination of the distribution and
occurrence of rare taxon of Lomatium
in northeastern California is far from resolved (cf. Soltis & Novak 1997, Gitzendanner
& Soltis 2001).